I haven't found any prefab coops that will work in our heat here in Texas. My husband built an open air coop/run combo (very similar to Carolina coop). Our local feed store (family-owned) occasionally has some coops ready built for purchase by a local craftsman. They are larger than prefab coops, and have good ventilation. -might check with a local feed/garden store and see if they have something like that. If you keep the one you have, definitely add vents - and I agree with the suggestion of removing the entire triangle and covering with hardware cloth. When it gets up over 100, I hook a mister to the water hose and plug in a fan or two aimed on the run. This keeps cool blowing on them.
Yep my coop is only solid on 3 sides. The whole front is open. The back wall is open 12 inches down from the roof all away across. I can close the front off easy enough with a tarp in the winter but so far I haven't needed to.